A simple guide to dermatoscopic diagnosis of melanocytic and nonmelanocytic skin lesions

Figure 1. Pigment network

Figure 2. Pigment network

Figure 3. Aggregated globules and pigment network

Figure 4. Aggregated globules

Figure 5. Streaks (radial streaming)

Figure 6. Pseudopods and regression (white and blue areas)

Figure 7. Regular streaks

Figure 8. Streaks (pseudopods).

Figure 9. Homogeneous blue pigmentation

Figure 10. Parallel furrow pattern

Figure 11. Parallel ridge pattern

Figure 12. Dots

Figure 13. Regression structures (blue areas are melanosis, white areas are fibrosis)

Figure 14. Blue-whitish veil

Figure 15. Blotches, pigment network, streaks and regression

Figure 16. Hypopigmentation.

Figure 17. Multiple milia-like cysts

Figure 18. Comedo-like openings

Figure 19. Fissures/ridges with a brain-like appearance

Figure 20. Light brown fingerprint-like structures

Figure 21. Moth-eaten border

Figure 22. Jelly-like border

Figure 23. Vascular pattern with hairpin vessels

Figure 24. Leaf-like structures.

Figure 25. Large blue-gray ovoid nests

Figure 26. Multiple blue-gray globules

Figure 27. Spoke wheel areas

Figure 28. Vascular pattern with arborizing vessels

Figure 29. Ulceration

Figure 30. Lacunar pattern

Figure 31. Dots, globules, blue-whitish veil and streaks.

Dermoscopy is a noninvasive diagnostic technique for the in vivo observation of pigmented skin lesions. It has been shown that the use of this technique improves the diagnostic accuracy of pigmented skin lesions when compared with clinical examination. One of the most important applications of dermoscopy is for the early diagnosis of melanoma (melanocytic lesion), which can occasionally resemble other nonmelanocytic lesions, such as seborrheic keratosis, basal cell carcinoma and vascular lesions. At present, dermoscopy is performed using a two-step procedure. The first step is to differentiate between melanocytic and nonmelanocytic lesions and the second is to differentiate benign melanocytic lesions from melanoma.

Differentiation between melanocytic & nonmelanocytic skin lesions

Dermoscopy allows the better visualization of anatomic structures of the epidermis, dermoepidermal junction and superficial papillary dermis, eliminating the surface reflection of the stratum corneum and rendering it translucent by different methods (e.g., oil and incident light magnification, polarized light and computerized systems). It is a link between macroscopic clinical dermatology and microscopic dermatopathology. This tool provides us with new morphological criteria for the differentiation of melanoma from other melanocytic and nonmelanocytic pigmented skin lesions [1–6]. It has been shown that the use of this technique improves the diagnostic accuracy of pigmented skin lesions when compared with clinical examination [7,8]. One of the most important applications of dermoscopy is for the early diagnosis of melanoma (melanocytic lesion), which can occasionally look similar to other nonmelanocytic lesions, such as seborrheic keratosis, basal cell carcinoma and vascular lesions.

Following the Consensus Net Meeting on Dermoscopy in July, 2000, dermoscopy is performed using a two-step procedure. The first step is to differentiate between melanocytic and nonmelanocytic lesions and the second is to differentiate benign melanocytic lesions from melanoma [9]. In order to perform this diagnosis, we need to know the different criteria for both melanocytic and nonmelanocytic lesions. Only then can we read the pigmented skin lesions with the dermoscope.

Main criteria for melanocytic lesions

The pigment network presents a grid-like appearance and consists of pigmented lines and hypopigmented holes. It represents the rete ridge pattern of the epidermis (Figures 1–3 & 15).

Aggregated globules are symmetrical, round and well-demarcated structures. They can be brown, black or red in color, and are usually larger than 0.1 mm (Figures 3,4 & 31).

Streaks are the expression of an altered network that becomes broken up. They are characterized by radial streaming and pseudopods.

Radial streaming refers to linear radial extensions of pigment than can appear at the periphery of a lesion.

Pseudopods are finger-like projections than can sometimes be seen at the periphery of the lesion into the normal skin (Figures 5–8,15 & 31).

Homogeneous blue pigmentation is present in some melanocytic lesions. They present blue-gray areas without structural components and there are pigmented cells in the dermis (Figure 9).

The parallel pattern criterion corresponds to acral melanocytic lesions. In this case, the pigmentation can follow the furrow or the ridge (Figures 10 & 11).

In benign melanocytic lesions, the pigmented cells cluster around the crista limitans pigmenting the furrow of the skin; while in melanoma, the pigmented cells cluster around the crista intermedia pigmenting the ridge. At present, the reason why this occurs remains unknown.

Further minor criteria that can be seen in melanocytic lesions

Dots are small, round structures (<0.1 mm). Their color can be black, brown, red or blue-gray, depending on the location of pigment accumulation (Figure 12).

Regression structures are white scar-like or blue-gray areas. Clinically, they correspond to a flat part of the lesion. The histopathological correlation of white areas is fibrosis, while for blue areas it is melanosis (Figures 6,13 & 15).

The blue-whitish veil is an irregular, structureless area of a confluent blue pigmentation with an overlying white ground-glass film. Clinically, it corresponds to an elevated part of the lesion (Figures 14 & 31).

Blotches are pigmented areas that can be localized or diffuse, and whose color can range from black to brown or gray (Figure 15).

Hypopigmentation can be areas with decreased pigmentation, which may be either diffuse or localized, focal or multifocal (Figure 16).

Criteria for seborrheic keratosis

Having discarded a melanocytic lesion, we need to determine whether or not it is a nonmelanocytic lesion, such as seborrheic keratosis, basal cell carcinoma or vascular lesion.

Multiple milia-like cysts are circular whitish-yellow areas. In larger seborrheic keratosisseborrheic keratosis, they show no typical circular shape (Figure 17). They are small in size (0.1–1 mm) and show no communication with the skin surface.

Comedo-like openings (irregular crypts) are small, circular, poro-like pseudo-follicular openings that communicate with the surface of the skin. They can be yellow, light brown, dark brown or black (Figure 18). Irregular crypts are large and irregular comedo-like openings that can be seen in large seborrheic keratosis.

Fissures/ridges (brain-like appearence) are size and shape variants of comedo-like openings (Figure 19).

Light brown fingerprint-like structures are tiny ridges running in parallel. They can usually be found at the periphery of the lesions in flat seborrheic keratosis (senile lentigines) (Figure 20).

Moth-eaten border is a concave border in which the pigment ends with a curved structure. This is known as Menzies’ sign and can usually be found in flat seborrheic keratosis (Figure 21). When this jelly-like border (jelly sign) is present, the pigment appears to be on the skin surface, with the appearance of a jelly spread onto the skin. It is usually found in flat seborrheic keratosis (Figure 22).

The typical vascular pattern is hairpin vessels (Figure 23).

Criteria for basal cell carcinoma

Once all these criteria have been investigated and none are present, a case of seborrheic keratosis can be discarded.

We now need to confirm that we are not in the presence of a basal cell carcinoma. In this case, we need to know and check the criteria for this particular lesion.

Leaf-like structures is the name given to gray-brown to slate-gray areas situated at the periphery of the lesion. They resemble fingers or maple leaves (Figure 24).

Large blue-gray ovoid nests are well-circumbscribed, confluent pigmented ovoid or elongated areas (Figure 25).

Multiple blue-gray globules are occasionally densely aggregated. It is important to differentiate them from multiple blue-gray dots or melanophages (Figure 26).

Spoke wheel areas are well-circumbscribed radial projections. They are blue, gray or brown in color and meet at an often darker (dark brown, black or blue) central axis (Figure 27).

A vascular pattern has the appearance of arborizing vessels, that is, telangiectases with tree-like branching (Figure 28).

Basal cell carcinoma is also more likely to be ulcerated than melanoma. We need to make sure that the ulceration is not due to recent trauma. It is usually a multiple event (Figure 29).

Vascular lesion criteria

Once melanocitic lesions, seborrheic keratosis and basal cell carcinoma are discarded as the cause, we proceed to check the possibility of a vascular lesion.

Lacunar patterns (red lagoons or red lacunas) are sharply demarcated oval areas with a reddish or red-bluish coloration due to increased and dilated vascular spaces within the papillary dermis (Figure 30).

If we have found none of the listed criteria, we are in the presence of a pigmented lesion with no specific criteria or unspecific pattern. We need to consider these lesions as melanocytic without specific pattern. Frequently, these unspecific pigmented lesions are melanomas.

If we are faced with a melanocytic lesion, we can now begin the second step in order to differentiate a benign melanocytic lesion from a melanoma.

There are different diagnosis methods we can use, such as pattern analysis [11], ABCD rule [14], seven-point checklist [15], 11-point checklist [16] and three-point checklist [17–18] among others.

Conclusion

In my opinion, dermoscopy is the best method for the early clinical diagnosis of melanoma. It is very important to train well in this technique.

Five-year view

Dermoscopy should be included in the resident program as an easy and inexpensive diagnosis method that has been proven to improve the clinical diagnosis of melanoma.